Classical trajectory study of the decomposition of HCOH⋅+ on a symmetry-invariant potential-energy surface

The unimolecular decomposition of HCOH⋅+ (and its deuterated analogs) to HCO+ and H⋅ has been studied using classical trajectories on a symmetry-invariant reaction path potential. The potential is based on an intrinsic reaction path of an ab initio Hartree–Fock surface. A group-theoretical procedure is applied to ensure that both hydrogens of HCOH⋅+ are treated equivalently. Classical trajectories on this surface show a nonequivalent distribution of products, the bias of which is mass dependent, despite rapid energy redistribution. The reaction mechanism and the role of energy redistribution are described, and a new interpretation of experimental data is proposed.